Tattooing has been practiced in most parts of the world for thousands of years. The earliest tattoos being discovered were those found on mummies dating back to 3300 B.C. In some cultures tattoos were thought to provide protection against sickness and misfortune. They would often signify one's rank or social status.
Today tattoos and tattooing is more popular than ever seeming to cross over every social, economic, and racial barrier. Still however some social stigma associated with tattoos remains. Until recently tattoos were considered permanent, preventing many from having them applied. Fortunately for those who no longer want their tattoos, there are methods of removal but those methods can be expensive, painful, and have less than satisfactory results.
The inks and dyes used were historically derived from substances found in nature and comprise a heterogeneous suspension of pigmented particles and other impurities. A well-known example is India ink, a suspension of carbon
Tattoos are produced by applying tattoo ink into the dermis, where the ink remains permanently. This technique introduces the pigment suspension through the skin by an alternating pressure-suction action caused by the elasticity of the skin in combination with the up-and-down movement of the needles. Water and other carriers for the pigment introduced into the skin diffuse through the tissues and are absorbed. The insoluble pigment particles are deposited in the dermis where initially placed, and remain, for the most part. Once the skin has healed, most pigment particles remain in the interstitial space of the tissue. Inks used for tattooing resist elimination by virtue of their inertness and the relatively large size of the insoluble pigment particles. A tattoo produced in this manner will partially fade over time and will generally remain present throughout the life of the tattooed person.
Unfortunately, there is currently no simple and successful way to remove tattoos. Removal by surgical excision, dermabrasion, or salabrasion requires invasive procedures associated with potential complications, such as infections, and usually results in conspicuous scarring. Removal by laser therapy is the most common technique and is usually limited to eliminating only from 50-70% of the tattoo pigment, resulting in a residual smudge. Laser removal requires multiple treatment sessions (usually five to twenty) with expensive equipment for maximal elimination. Thus, the overall cost of laser removal is generally prohibitively expensive.
Temporary substitutes for tattoos are unsatisfactory because they are very short-lived. If only the surface of the skin is colored, such as by a decalcomania-containing ink (henna tattoos) or by painting on the skin, the ornamentation is easily removed by wetting or rubbing the skin or by the natural sloughing of epidermis every three to four weeks. While this technique produces only temporary skin ornamentation, it would be desirable to have the option to color the skin to last longer than a few hours, days, or weeks.
Therefore there is a need for a system to apply a stable, indefinitely lasting tattoo while still having the means to remove the tattoo on demand with a simple, non-invasive treatment.